In case information is read/written from/into a disk-like optical recording medium (referred to as an “optical disk” hereinafter) such as CD, DVD, or the like in the optical disk device, a track on the optical disk must be scanned by moving an optical pickup in a radial direction (traverse direction) of the optical disk while rotating the optical disk by a spindle motor. As a feeding mechanism for the optical pickup in the radial direction of the disk, a stepping motor is often used recently. The stepping motor is suitable for the feeding mechanism for the optical pickup because such motor can take a position at a fine rotation angle in response to an applied pulse train and also make a fast feed by feeding the optical pickup as the object of drive in terms of a direct drive.
In the stepping motor, a rotor is rotated at a rotation angle that is proportional to the number of pulses applied as a driving current. FIG. 15 is a view showing a revolving speed-torque characteristic of the stepping motor. In FIG. 15, an abscissa denotes a pulse rate of a drive pulse signal supplied as the driving current, i.e., a revolving speed of the stepping motor, and an ordinate a torque of the stepping motor in operation. In a range (self-starting range) Ti below a pull-in torque, the stepping motor can start, stop, and reverse in synchronism with an applied drive pulse signal. Also, in a range To in excess of a pull-out torque, an out-of-step phenomenon occurs, so that the stepping motor cannot take a rotating action in synchronism with the drive pulse signal. Also, in a range (through range) Ts between the pull-in torque and the pull-out torque, the stepping motor can continue to rotate in synchronism with the drive pulse signal when such motor has already been rotated, nevertheless an out-of-step phenomenon takes place and the stepping motor cannot make a normal rotation when such motor is started from its stationary state. Since the stepping motor has the above-mentioned characteristics, a design that is made based upon a load torque is absolutely essential to the stepping motor.
As the feeding operation of the optical pickup, there are an operation for performing intermittently a feed of about several tens μm in reading or writing the information from or into the optical disk (referred to as an “optical axis correction feeding operation” hereinafter) and a seek operation for performing a feed at a high speed toward the designated track over a long distance. In general, a full step drive (two-phase excitation drive) is executed in the seek operation that needs a fast movement of the optical pickup, while a microstep drive is executed in the optical axis correction feeding operation that needs a fine feed control of about several tens μm.
In the optical axis correction feeding operation, in order to scan the track on the optical disk, an objective lens of the optical pickup moves in the traverse direction following to the track that is recorded spirally or concentrically on the optical disk. At this time, a tracking actuator of the optical pickup executes position control of the objective lens with respect to the track of the optical disk. Since a movable range of the tracking actuator of the optical pickup is limited, the stepping motor is controlled in such a manner that, when the objective lens is shifted from a center of a base of the optical pickup by a predetermined amount, the base of the optical pickup is moved in about several tens μm in the traverse direction to cancel a shifted amount.
In the optical axis correction feeding operation, the stepping motor executes the feeding operation in the microstep drive. As shown in FIG. 16, in the microstep drive, a driving current like a sinusoidal wave is applied to respective terminals of the stepping motor to rotate the motor smoothly at a rotation angle smaller than a step angle peculiar to each motor. The microstep drive can make an infinitesimal feed of the optical pickup while suppressing generation of a vibration.
In the stepping motor, when the microstep drive is carried out in the form of continuous current supply, a consumption power is increased and also generation of heat is increased. Thus, such a problem arose that the life of parts is shortened or an operating temperature limit of the drive must be restricted. Therefore, the optical disk device for controlling the drive of the stepping motor by applying a driving current for the microstep drive only in predetermined time (several msec) is known (see Patent Literature 1, for example).
The optical axis correction feeding operation is continued during the reading or writing operation of the information from or into the optical disk, while the stepping motor is controlled such that the stepping motor is driven to cancel a shifted amount when a predetermined shift of the objective lens is generated. In other words, an operation of driving the stepping motor is repeated every time when a lens shift of the objective lens is generated, so that the information can be read correctly by driving intermittently the stepping motor.
Patent Literature 1: JP-A-10-149639
Disclosure of the Invention
Problems that the Invention is to Solve
However, when an operating temperature range of the optical disk device is broad in an onboard application, or the like, a mechanical load characteristic is changed following upon a change of temperature. Therefore, even in the device that operates normally at an ordinary temperature, the load was increased at a low temperature due to the influence of a grease viscosity, and in some cases the stepping motor produced an out-of-step phenomenon and was unable to take a normal operation.
For this reason, the measure should be taken, e.g., an expensive grease that has a less variation in the temperature characteristic should be employed, a performance guarantee temperature range should be limited in operation, or the like. Therefore, it is difficult to accomplish the high-performance inexpensive device whose operating temperature range is board. In particular, in the case of the onboard optical disk device employed as the onboard audio-visual equipment, the navigation system, or the like, it is feared that the above phenomenon becomes actual because such equipment is often used in the low temperature environment.
The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide an optical disk device capable of stabilizing a feeding operation of an optical pickup even in a broad operating temperature environment in an optical pickup driving mechanism using a stepping motor.
Means for Solving the Problems
First, an optical disk device of the present invention, includes an optical pickup for reading information recorded on an optical disk; a stepping motor for moving the optical pickup in a radial direction of the optical disk; a driving current supplying unit for supplying a driving current to drive the stepping motor, and executing a microstep drive; a temperature sensing unit for sensing an ambient temperature of the optical pickup; and a drive controlling unit for executing drive control of the stepping motor by changing the driving current applied in the microstep drive in response to the sensed ambient temperature.
Accordingly, the driving current of the stepping motor in executing the microstep drive is changed in response to the ambient temperature. Therefore, the stepping motor can be driven by the appropriate torque in answer to the load that changes depending on the temperature, and also the feeding operation of the optical pickup can be stabilized in the broad operating temperature environment.
Also, second, as one mode of the present invention, the driving current supplying unit supplies an intermittent driving current at a predetermined time width to the stepping motor in executing the microstep drive, and the drive controlling unit changes a supply time width of the driving current in response to the ambient temperature.
Accordingly, the supply time width of the driving current is changed in response to the ambient temperature. Therefore, the stepping motor can be driven by the appropriate torque that agrees with the load that changes depending on the temperature, and also the optical disk device can be used in the broad operating temperature environment by preventing occurrence of the defective operation in reading/writing the information.
Also, third, as one mode of the present invention, the drive controlling unit changes the supply time width of the driving current into an increased value when the ambient temperature is equal to or lower than a predetermined temperature.
Accordingly, the supply time width of the driving current is increased when the ambient temperature is equal to or lower than a predetermined temperature. Therefore, the stepping motor can be driven by the appropriate torque in answer to the load that is increased in a low temperature range.
Also, fourth, the optical disk device of the present invention, further includes a temperature coefficient translation table for storing a temperature coefficient corresponding to the ambient temperature; wherein the drive controlling unit calculates the temperature coefficient corresponding to the ambient temperature by using the temperature coefficient translation table, and decides the supply time width of the driving current.
Therefore, the appropriate supply time width of the driving current can be set by using the temperature coefficient that corresponds to the ambient temperature, and also the stepping motor can be driven by the appropriate torque in compliance with the ambient temperature.
Also, fifth, an optical disk device of the present invention, includes an optical pickup for reading information recorded on an optical disk; a stepping motor for moving the optical pickup in a radial direction of the optical disk; a driving current supplying unit for supplying a driving current to drive the stepping motor, and executing selectively a full step drive and a microstep drive; a full step drive deciding unit for deciding whether or not an operation taken when the optical pickup is moved in the full step drive is normally ended; and a drive controlling unit for executing drive control of the stepping motor by changing the driving current applied in the microstep drive in response to a decision result.
Accordingly, the driving current applied in the microstep drive of the stepping motor is changed in response to the decision result indicating whether or not the optical pickup moving operation in the full step drive has been normally ended. Therefore, the stepping motor can be driven by the torque that is appropriate for the load that changes depending on the temperature, and also the feeding operation of the optical pickup can be stabilized in the broad operating temperature environment.
Also, sixth, the optical disk device of the present invention further includes a driving current changing unit for changing the driving current applied in the full step drive.
Therefore, it is possible to decide whether or not the optical pickup moving operation will be normally ended, by changing the driving current applied in the full step drive.
Also, seventh, as one mode of the present invention, the driving current changing unit changes stepwise a current amplitude of the driving current applied in the full step drive.
Therefore, it is possible to decide whether or not the optical pickup moving operation will be normally ended, in response to the current amplitude value when the current amplitude of the driving current applied in the full step drive is changed stepwise.
Also, eighth, the optical disk device of the present invention further includes a normal driving current amplitude deciding unit for deciding a current amplitude value of the driving current by which a feeding operation in the full step drive is normally executed; and wherein the driving current supplying unit supplies an intermittent driving current at a predetermined time width to the stepping motor in executing the microstep drive, and the drive controlling unit changes a supply time width of the driving current in response to the current amplitude width of the driving current.
Accordingly, the supply time width of the driving current applied in the microstep drive is changed in response to the current amplitude value of the driving current by which the feeding operation in the full step drive can be normally executed. Therefore, the stepping motor can be driven by the appropriate torque that agrees with the load that changes depending on the temperature, and also the optical disk device can be used in the broad operating temperature environment by preventing occurrence of the defective operation in reading/writing the information.
Also, ninth, the optical disk device of the present invention further includes an optical pickup position sensing unit for sensing whether or not a movement of the optical pickup to a predetermined position of an inner circumference of the optical disk is completed; and a moving complete current amplitude deciding unit for deciding a current amplitude value of the driving current such that the movement of the optical pickup to the predetermined position of the inner circumference of the optical disk is completed within a predetermined time in the full step drive; wherein the driving current supplying unit supplies an intermittent driving current at a predetermined time width to the stepping motor in executing the microstep drive, and the drive controlling unit changes a supply time width of the driving current in response to the current amplitude value of the driving current.
Accordingly, the supply time width of the driving current applied in the microstep drive is changed in response to the current amplitude value of the driving current decided in such a manner that the movement of the optical pickup to the predetermined position of the inner circumference is completed within the predetermined time in the full step drive. Therefore, the stepping motor can be driven by the appropriate torque that agrees with the load that changes depending on the temperature, and also the optical disk device can be used in the broad operating temperature environment by preventing occurrence of the defective operation in reading/writing the information.
Also, tenth, as one mode of the present invention, the drive controlling unit changes the supply time width of the driving current into an increased value when the current amplitude value is equal to or greater than a predetermined value.
Accordingly, the supply time width of the driving current is increased when the current amplitude value of the driving current decided such that the feeding operation in the full step drive can be normally executed is equal to or smaller than a predetermined value. Therefore, the stepping motor can be driven by the appropriate torque in answer to the load that is increased in the low temperature range, or the like, for example.
Also, eleventh, the optical disk device of the present invention further includes an optical pickup position sensing unit for sensing whether or not a movement of the optical pickup to a predetermined position of an inner circumference of the optical disk is completed; and a moving time deciding unit for deciding a moving time required until the optical pickup is moved to the predetermined position of the inner circumference in the full step drive; wherein the driving current supplying unit supplies an intermittent driving current at a predetermined time width to the stepping motor in executing the microstep drive, and the drive controlling unit changes a supply time width of the driving current in response to the moving time of the optical pickup.
Accordingly, the supply time width of the driving current applied in the microstep drive is changed in response to the moving time required until the optical pickup is moved to the predetermined position of the inner circumference in the full step drive. Therefore, the stepping motor can be driven by the appropriate torque that agrees with the load that changes depending on the temperature, and also the optical disk device can be used in the broad operating temperature environment by preventing occurrence of the defective operation in reading/writing the information.
Also, twelfth, as one mode of the present invention, the drive controlling unit changes the supply time width of the driving current into an increased value when the moving time is equal to or longer than a predetermined value.
Accordingly, the supply time width of the driving current is increased when the moving time required until the optical pickup is moved to the predetermined position of the inner circumference in the full step drive is equal to or longer than the predetermined value. Therefore, the stepping motor can be driven by the appropriate torque in answer to the load that is increased in the low temperature range, or the like, for example.
Also, thirteenth, an optical disk device of the present invention, includes an optical pickup for reading information recorded on an optical disk; a stepping motor for moving the optical pickup in a radial direction of the optical disk; a driving current supplying unit for supplying a driving current to drive the stepping motor, executing selectively a full step drive and a microstep drive, and supplying an intermittent driving current at a predetermined time width to the stepping motor in executing the microstep drive; a driving current changing unit for changing a pulse rate of the driving current applied in the full step drive; a full step drive deciding unit for deciding whether or not an operation taken when the optical pickup is moved in the full step drive is normally ended; and a drive controlling unit for executing drive control of the stepping motor by changing a supply time width of the driving current applied in the microstep drive in response to a decision result.
Accordingly, the driving current applied in the microstep drive of the stepping motor is changed in response to the decision result indicating whether or not the optical pickup moving operation in the full step drive has been completed normally. Therefore, the stepping motor can be driven by the torque that is appropriate for the load that changes depending on the temperature, and also the feeding operation of the optical pickup can be stabilized in the broad operating temperature environment.
Also, fourteenth, as one mode of the present invention, the driving current changing unit changes stepwise the pulse rate of the driving current in executing the full step drive.
Therefore, it is possible to decide whether or not the optical pickup moving operation will be normally ended, in response to a pulse rate value when the pulse rate of the driving current applied in the full step drive is changed stepwise.
Also, fifteenth, the optical disk device of the present invention further includes a normal drive pulse rate deciding unit for deciding the pulse rate of the driving current such that a feeding operation is normally executed in the full step drive; and wherein the drive controlling unit changes the supply time width of the driving current in response to the pulse rate of the driving current.
Accordingly, the supply time width of the driving current applied in the microstep drive is changed in response to the pulse rate of the driving current by which the feeding operation in the full step drive can be normally executed. Therefore, the stepping motor can be driven by the appropriate torque that agrees with the load that changes depending on the temperature, and also the optical disk device can be used in the broad operating temperature environment by preventing occurrence of the defective operation in reading/writing the information.
Also, sixteenth, the optical disk device of the present invention further includes an optical pickup position sensing unit for sensing whether or not a movement of the optical pickup to a predetermined position of an inner circumference of the optical disk is completed; and a moving complete pulse rate deciding unit for deciding the pulse rate of the driving current such that the movement of the optical pickup to the predetermined position of the inner circumference of the optical disk is completed within a predetermined time in the full step drive; wherein the drive controlling unit changes the supply time width of the driving current in response to the pulse rate of the driving current.
Accordingly, the supply time width of the driving current applied in the microstep drive is changed in response to the pulse rate of the driving current decided in such a manner that the movement of the optical pickup to the predetermined position of the inner circumference is completed in the full step drive within the predetermined time. Therefore, the stepping motor can be driven by the appropriate torque that agrees with the load that changes depending on the temperature, and also the optical disk device can be used in the broad operating temperature environment by preventing occurrence of the defective operation in reading/writing the information.
Also, seventeenth, as one mode of the present invention, the drive controlling unit changes the supply time width of the driving current into an increased value when the pulse rate is equal to or smaller than a predetermined value.
Accordingly, the supply time width of the driving current is increased when the pulse rate of the driving current decided such that the feeding operation in the full step drive can be normally executed is equal to or smaller than a predetermined value. Therefore, the stepping motor can be driven by the appropriate torque in answer to the load that is increased in the low temperature range, or the like, for example.
Also, eighteenth, the optical disk device of the present invention further includes an optical pickup position sensing unit for sensing whether or not a movement of the optical pickup to a predetermined position of an inner circumference of the optical disk is completed; and a moving time deciding unit for deciding a moving time required until the optical pickup is moved to the predetermined position of the inner circumference in the full step drive; wherein the drive controlling unit changes the supply time width of the driving current in response to the moving time of the optical pickup.
Accordingly, the supply time width of the driving current applied in the microstep drive is changed in response to the moving time required until the optical pickup is moved to the predetermined position of the inner circumference in the full step drive. Therefore, the stepping motor can be driven by the appropriate torque that agrees with the load that changes depending on the temperature, and also the optical disk device can be used in the broad operating temperature environment by preventing occurrence of the defective operation in reading/writing the information.
Also, nineteenth, as one mode of the present invention, the drive controlling unit changes the supply time width of the driving current into an increased value when the moving time is equal to or longer than a predetermined value.
Accordingly, the supply time width of the driving current is increased when the moving time required until the optical pickup is moved to the predetermined position of the inner circumference in the full step drive is equal to or longer than the predetermined value. Therefore, the stepping motor can be driven by the appropriate torque in answer to the load that is increased in the low temperature range, or the like, for example.
Also, twentieth, as one mode of the present invention, a decision regarding a drive of the optical pickup in the full step drive is made during an inner circumferential feeding operation that is applied to initialize a position of the optical pickup immediately after the optical disk device is started.
Therefore, the driving current applied in the microstep drive can be controlled by making the decision regarding the drive of the optical pickup in the full step drive, e.g., whether the operation taken when the optical pickup is moved in the full step drive upon initializing a position of the optical pickup immediately after the optical disk device is started is normally ended or not, or the like.
Also, twenty-first, an onboard equipment of the present invention includes an optical disk device.
In particular, in the onboard equipment used in the broad temperature range such as the low temperature environment, and the like, when the above optical disk device is applied to the equipment, the feeding operation of the optical pickup can be stabilized irrespective of the ambient temperature and also occurrence of the operational failure can be prevented.
Advantages of the Invention
According to the present invention, an optical disk device capable of stabilizing a feeding operation of an optical pickup even in a broad operating temperature environment in an optical pickup driving mechanism using a stepping motor can be provided.